Ice Body is an ability introduced in generation 4.
19 Pokémon can have this ability, such as Snorunt, Glalie, Spheal, Sealeo and Walrein. For 8 of them it is the hidden ability, usually obtained from events, raids or breeding.
Official effect
Heals for 1/16 max HP after each turn during hail. Protects against hail damage.